Under certain operating conditions, aircraft are vulnerable to accumulation of ice on component surfaces such as propellers, air intake, and the wings. If left unchecked, this ice accumulation can laden the aircraft with so much additional weight that the component configuration, e.g., the airfoil configuration of the wings or other aerodynamic properties, are altered. This can cause undesirable and dangerous flying conditions. Ice protection systems on aircraft are thus required to ensure safety of flight, regardless of the environmental conditions experienced.
A variety of systems have been proposed for removing ice from aircraft during flight or for preventing its initial accumulation on the leading edge surfaces.
For example, some systems seek to remove ice once it has formed. These systems may be referred to as “de-icing” systems. Other systems seek to prevent the accumulation of ice altogether in the first place. These systems may be referred to as “anti-icing” systems. Although an anti-icing mode may ensure high aircraft performances by avoiding any ice accretion on the external surface protected, an anti-icing mode is more energy-consuming and requires continuous operating of the anti-icing zone(s). By contrast, a de-icing mode generally removes ice from the desired surface according to pre-defined cycles (activation periods) that are compatible with a maximum ice thickness acceptable to conserve surface performances. The protection mode is often chosen according to performance losses acceptable, as well as according to power available on the aircraft. These various systems can be categorized as thermal, chemical, or mechanical.
Thermal anti-icers or de-icers primarily use a joule/heating effect to maintain a surface at a sufficient temperature to avoid ice or to remove it. Heat may be applied through a heating element or via heated gasses that are circulated. The heat can either prevent the accumulation of ice or it can melt/loosen ice that has formed. Once loosened, the ice is generally blown from the aircraft.
For chemical de-icing, a chemical compound may be applied to all or a part of the surface to be protected. This may limit adhesion of the ice or it may alter the freezing point of water collecting on the surface.
Mechanical de-icers often use actuators to deform the external surface to remove ice. These methods generally require a minimum ice thickness to be efficient. Additionally, surface deformation maintained over a long period can impact aerodynamic performance of the surface to be protected. One example of a mechanical de-icer uses air chambers or tube-like structures that are embedded into an elastomeric assembly. The air chambers can be inflated in order to deform the surface. Upon inflation, the air chambers expand the leading edge profile and cause cracking of the ice. Inflation time is usually a few seconds or longer. Such de-icers can be installed behind an erosion shied in order to improve environmental resistance. They generally extend the entire span of the wing or surface to be protected from ice. These systems are often referred to as pneumatic boots.
Another example of a mechanical de-icer system is an electromagnetic system. These systems include a magnetic coil installed between an aircraft structure and an erosion shield, and an electronic system to generate an electrical impulse to activate a coil. The coils can be spaced so that when the coils are activated, a torsional wave mode deformation of the skin can occur, which causes ice removal. In another example, a deflection wave mode deformation can be generated in the skin by activation of two electro-magnetic coils. Although improvement attempts have been made, further improvements to de-icing systems and technologies are desirable.